Nuclear reactor system, transmitter device therefor, and associated method of measuring environmental conditions

ABSTRACT

A transmitter device includes a neutron detector structured to detect neutron flux, a capacitor electrically connected in parallel with the neutron detector, a gas discharge tube having an input end and an output end, and an antenna electrically connected to the output end. The input end is electrically connected with the capacitor. The antenna is structured to emit a signal corresponding to the neutron flux.

BACKGROUND Field

The disclosed concept pertains generally to nuclear reactor systems. Thedisclosed concept also pertains to transmitter devices for nuclearreactor systems. The disclosed concept further pertains to methods ofmeasuring environmental conditions with a transmitter device.

Background Information

In many state-of-the-art nuclear reactor systems in-core sensors areemployed for measuring the radioactivity within the core at a number ofaxial elevations. These sensors are used to measure the radial and axialdistribution of the power inside the reactor core. This powerdistribution measurement information is used to determine whether thereactor is operating within nuclear power distribution limits. Thetypical in-core sensor used to perform this function is a self-powereddetector that produces an electric current that is proportional to theamount of fission occurring around it. This type of sensor does notrequire an outside source of electrical power to produce the current andis commonly referred to as a self-powered detector and is more fullydescribed in U.S. Pat. No. 5,745,538, issued Apr. 28, 1998, and assignedto the Assignee of this invention. FIG. 1 provides a diagram of themechanisms that produce the current I(t) in a self-powered detectorelement 10. A neutron sensitive material such a vanadium is employed forthe emitter element 12 and emits electrons in response to neutronirradiation. Typically, the self-powered detectors are grouped withininstrumentation thimble assemblies. A representative in-coreinstrumentation thimble assembly 16 is shown in FIG. 2. The signal levelgenerated by the essentially non-depleting neutron sensitive emitter 12shown in FIG. 1 is low, however, a single, full core length neutronsensitive emitter element provides an adequate signal without complexand expensive signal processors. The proportions of the full lengthsignal generated by the single neutron sensitive emitter elementattributable to various axial regions of the core are determined fromapportioning the signal generated by different lengths of gammasensitive elements 14 which define the axial regions of the core and areshown in FIG. 2. The apportioning signals are ratioed which eliminatesmuch of the effects of the delayed gamma radiation due to fissionproducts. The in-core instrumentation thimble assemblies also include athermocouple 18 for measuring the temperature of the coolant exiting thefuel assemblies. The electrical signal output from the self-powereddetector elements and the thermocouple in each in-core instrumentationthimble assembly in the reactor core are collected at the electricalconnector 20 and sent to a location well away from the reactor for finalprocessing and use in producing the measured core power distribution.

FIG. 3 shows an example of a core monitoring system presently offeredfor sale by Westinghouse Electric Company LLC, Cranberry, Pa., with aproduct name WINCISE™ that employs fixed in-core instrumentation thimbleassemblies 16 within the instrument thimbles of the fuel assemblieswithin the core to measure the core's power distribution. Cabling 22extends from the instrument thimble assemblies 16 through thecontainment seal table 24 to a single processing cabinet 26 where theoutputs are conditioned, digitized and multiplexed and transmittedthrough the containment walls 28 to a computer workstation 30 where theycan be further processed and displayed. The thermocouple signals fromthe in-core instrumentation thimble assemblies are also sent to areference junction unit 32 which transmits the signals to an inadequatecore cooling monitor 34 which communicates with the plant computer 36which is also connected to the workstation 30. Because of the hostileenvironment within the containment walls 28, the signal processingcabinet 26 has to be located a significant distance away from the coreand the signal has to be sent from the detectors 16 to the signalprocessing cabinet 26 through specially constructed cables that areextremely expensive and the long runs reduce the signal to noise ratio.Unfortunately, these long runs of cable have proved necessary becausethe electronics for signal processing has to be shielded from the highlyradioactive environment surrounding the core region.

In previous nuclear plant designs, the in-core detectors entered thereactor vessel from the lower hemispherical end and entered the fuelassemblies' instrument thimble from the bottom fuel assembly nozzle. Inat least some of the current generation of nuclear plant designs, suchas the AP1000 nuclear plant, the in-core monitoring access is located atthe top of the reactor vessel, which means that during refueling allin-core monitoring cabling will need to be removed before accessing thefuel. A wireless in-core monitor that is self-contained within the fuelassemblies and wirelessly transmits the monitored signals to a signalreceiver positioned inside the reactor vessel but away from the fuelwould allow immediate access to the fuel without the time-consuming andexpensive process of disconnecting, withdrawing and storing the in-coremonitoring cables before the fuel assemblies could be accessed, andrestoring those connections after the refueling process is complete. Awireless alternative would thus save days in the critical path of arefueling outage. A wireless system also allows every fuel assembly tobe monitored, which significantly increases the amount of core powerdistribution information that is available.

However, a wireless system requires that electronic components belocated at or near the reactor core where gamma and neutron radiationand high temperatures would render semi-conductor electronics inoperablewithin a very short time. Vacuum tubes are known to be radiationinsensitive, but their size and electric current demands have made theiruse impractical until recently. Recent developments inmicro-electromechanical devices have allowed vacuum tubes to shrink tointegrated circuit component sizes and significantly reduce power drawdemands. Such a system is described in U.S. patent application Ser. No.12/986,242, entitled “Wireless In-core Neutron Monitor,” filed Jan. 7,2011. The primary electrical power source for the signal transmittingelectrical hardware for the embodiment disclosed in the afore-notedpatent application is a rechargeable battery shown as part of anexemplary power supply. The charge on the battery is maintained by theuse of the electrical power produced by a dedicated power supplyself-powered detector element that is contained within the power supply,so that the nuclear radiation in the reactor is the ultimate powersource for the device and will continue so long as the dedicated powersupply self-powered detector element is exposed to an intensity ofradiation experienced within the core.

Accordingly, one object of this disclosed concept is to provide amechanism to transmit data of environmental conditions within aninstrument thimble of a fuel assembly to a remote location.

SUMMARY

These needs and others are met by the disclosed concept, which aredirected to an improved nuclear reactor system, transmitter devicetherefor, and associated method of measuring a number of environmentalconditions.

As one aspect of the disclosed concept, a transmitter device includes aneutron detector structured to detect neutron flux, a capacitorelectrically connected in parallel with the neutron detector, a gasdischarge tube having an input end and an output end, and an antennaelectrically connected to the output end. The input end is electricallyconnected with the capacitor. The antenna is structured to emit a signalcorresponding to the neutron flux.

As another aspect of the disclosed concept, a nuclear reactor systemincluding a fuel assembly having an instrument thimble, and theaforementioned transmitter device is provided.

As another aspect of the disclosed concept, a method of measuring anumber of environmental conditions with the aforementioned transmitterdevice is provided. The method includes the steps of detecting neutronflux with the neutron detector; storing energy in the capacitor until abreakdown voltage of the gas discharge tube is reached; and emitting asignal with the antenna corresponding to the neutron flux.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic representation of a self-powered radiationdetector;

FIG. 2A is a plan view of an in-core instrument thimble;

FIG. 2B is a schematic view of the interior of the forward sheath of thein-core instrument thimble assembly of FIG. 2A;

FIG. 2C is a sectional view of the electrical connector at the rear endof the in-core instrument thimble assembly of FIG. 2A;

FIG. 3 is a schematic layout of an in-core monitoring system;

FIG. 4 is a simplified schematic of a nuclear reactor system;

FIG. 5 is an elevational view, partially in section, of a nuclearreactor vessel and interior components;

FIG. 6 is an elevational view, partially in section, of a nuclear fuelassembly that contains an in-core nuclear instrument thimble assembly;

FIG. 7 is a schematic circuitry diagram of a transmitter device, inaccordance with one non-limiting embodiment of the disclosed concept;

FIG. 8 is a graph showing voltage at a location in the transmitterdevice of FIG. 7 versus time;

FIG. 9 is a graph showing voltage at another location in the transmitterdevice of FIG. 7 versus time;

FIG. 10 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept;

FIG. 11 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept;

FIG. 12 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept; and

FIG. 13 is a schematic circuitry diagram of another transmitter device,in accordance with another non-limiting embodiment of the disclosedconcept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The primary side of nuclear power generating systems which are cooledwith water under pressure comprises a closed circuit which is isolatedfrom and in heat exchange relationship with a secondary side for theproduction of useful energy. The primary side comprises the reactorvessel enclosing a core internal structure that supports a plurality offuel assemblies containing fissile material, the primary circuit withinheat exchange steam generators, the inner volume of a pressurizer, pumpsand pipes for circulating pressurized water; the pipes connecting eachof the steam generators and pumps to the reactor vessel independently.Each of the parts of the primary side comprising a steam generator, apump and a system of pipes which are connected to the reactor vesselform a loop of the primary side.

For the purpose of illustration, FIG. 4 shows a simplified nuclearreactor system, including a generally cylindrical pressure vessel 40,having a closure head 42 enclosing a nuclear core 44. A liquid reactorcoolant, such as water, is pumped into the vessel 40 by pump 46 throughthe core 44 where heat energy is absorbed and is discharged to a heatexchanger 48, typically referred to as a steam generator, in which heatis transferred to a utilization circuit (not shown), such as a steamdriven turbine generator. The reactor coolant is then returned to thepump 46 completing the primary loop. Typically, a plurality of theabove-described loops are connected to a single reactor vessel 40 byreactor coolant piping 50.

An exemplary reactor design to which this invention can be applied isillustrated in FIG. 5. In addition to the core 44 comprised of aplurality of parallel, vertical, co-extending fuel assemblies 80, forpurpose of this description, the other vessel internal structures can bedivided into the lower internals 52 and the upper internals 54. Inconventional designs, the lower internals' function is to support, alignand guide core components and instrumentation as well direct flow withinthe vessel. The upper internals 54 restrain or provide a secondaryrestraint for the fuel assemblies 80 (only two of which are shown forsimplicity in this figure), and support and guide instrumentation andcomponents, such as control rods 56. In the exemplary reactor shown inFIG. 5, coolant enters the reactor vessel 40 through one or more inletnozzles 58, flows down through an annulus between the reactor vessel 40and the core barrel 60, is turned 180° in a lower reactor vessel plenum61, passes upwardly through a lower support plate and a lower core plate64 upon which the fuel assemblies 80 are seated, and through and aboutthe assemblies. In some designs, the lower support plate 62 and thelower core plate 64 are replaced by a single structure, the lower coresupport plate that has the same elevation as 62. Coolant exiting thecore 44 flows along the underside of the upper core plate 66 andupwardly and through a plurality of perforations 68 in the upper coreplate 66. The coolant then flows upwardly and radially to one or moreoutlet nozzles 70.

The upper internals 54 can be supported from the vessel or the vesselhead 42 and includes an upper support assembly 72. Loads are transmittedbetween the upper support assembly 72 and the upper core plate 66primarily by a plurality of support columns 74. Each support column isaligned above a selected fuel assembly 80 and perforations 68 in theupper core plate 66.

The rectilinearly movable control rods 56 typically include a driveshaft 76 and a spider assembly 78 of neutron poison rods that are guidedthrough the upper internals 54 and into aligned fuel assemblies 80 bycontrol rod guide tubes 79.

FIG. 6 is an elevational view represented in vertically shortened form,of a fuel assembly being generally designated by reference character 80.The fuel assembly 80 is the type used in a pressurized water reactor,such as the reactor of FIG. 5, and has a structural skeleton which atits lower end includes a bottom nozzle 82. The bottom nozzle 82 supportsthe fuel assembly on the lower core support plate 64 in the core regionof the nuclear reactor. In addition to the bottom nozzle 82, thestructural skeleton of the fuel assembly 80 also includes a top nozzle84 at its upper end and a number of guide tubes or thimbles 86 whichextend longitudinally between the bottom and top nozzles 82 and 84 andat opposite ends are rigidly attached thereto.

The fuel assembly 80 further includes a plurality of transverse grids 88axially spaced along and mounted to the guide thimbles 86 (also referredto as guide tubes) and an organized array of elongated fuel rods 90transversely spaced and supported by the grids 88. Although it cannot beseen in FIG. 6, the grids 88 are conventionally formed from orthogonalstraps that are interleaved in an egg-crate pattern with the adjacentinterface of four straps defining approximately square support cellsthrough which the fuel rods 90 are supported in transversely spacedrelationship with each other. In many conventional designs, springs anddimples are stamped into the opposing walls of the straps that form thesupport cells. The springs and dimples extend radially into the supportcells and capture the fuel rods therebetween; inserting pressure on thefuel rod cladding to hold the rods in position. Also, the assembly 80has an instrumentation tube 92 located in the center thereof thatextends between and is mounted to the bottom and top nozzles 82 and 84.With such an arrangement of parts, the fuel assembly 80 forms anintegral unit capable of being conveniently handled without damaging theassembly of parts.

As mentioned above, the fuel rods 90 in the array thereof in theassembly 80 are held in spaced relationship with one another by thegrids 88 spaced along the fuel assembly length. Each fuel rod 90includes a plurality of nuclear fuel pellets 94 and is closed at itsopposite ends by upper and lower end plugs 96 and 98. The fuel pellets94 are maintained in a stack by a plenum spring 100 disposed between theupper end plug 96 in the top of the pellet stack. The fuel pellets 94,composed of fissile material, are responsible for creating the reactivepower of the reactor. The cladding, which surrounds the pellets,functions as a barrier to prevent fission byproducts from entering thecoolant and further contaminating the reactor system.

To control the fission process, a number of control rods 56 arereciprocally movable in the guide thimbles 86 located at predeterminedpositions in the fuel assembly 80. Specifically, a rod cluster controlmechanism (also referred to as a spider assembly) 78 positioned abovethe top nozzle 84 supports the control rods 56. The rod cluster controlmechanism has an internally threaded cylindrical hub member 102 with aplurality of radially extending flukes or arms 104 that with the controlrods 56 form the spider assembly 78 that was previously mentioned withrespect to FIG. 5. Each arm 104 is interconnected to the control rods 56such that the control mechanism 78 is operable to move the control rodsvertically in the guide thimbles to thereby control the fission processin the fuel assembly 80, under the motor power of control rod driveshafts 76 (shown in FIG. 5) which are coupled to the control rod hubs102, all in a well known manner.

FIG. 7 shows a schematic circuitry diagram of a transmitter device 200,in accordance with one non-limiting embodiment of the disclosed concept.The example transmitter device 200 is preferably located within one ofthe instrument thimbles 86 of the fuel assembly of FIG. 6. As will bediscussed in greater detail hereinbelow, the transmitter device 200allows an environmental condition (e.g., without limitation, neutronflux) within the instrument thimble 86 (FIG. 6) to be monitoredwirelessly.

The example transmitter device 200 includes a self-powered neutrondetector 210, a first capacitor 212 electrically connected in parallelwith the neutron detector 210, a gas discharge tube 214, an antenna 220,and an oscillator circuit 222. One example of a suitable gas dischargetube that may be employed in the disclosed concept is presently offeredfor sale by Littlefuse, Inc., of Chicago, Ill., and has a product nameGas Discharge Tube. The gas discharge tube 214 has an input end 216 andan output end 218. In one example embodiment, the gas discharge tube 214is designed as a spark gap device wherein an arc, or spark, occurs whenthe input end 216 is electrically connected with the output end 218. Inanother example embodiment, the gas discharge tube 214 is designed tooperate with a relatively less intense glow discharge occurring when theinput end 216 electrically connects with the output end 218. The inputend 216 is electrically connected with the first capacitor 212, and theoutput end 218 is electrically connected with the antenna 220. As shown,the oscillator circuit 222 includes a second capacitor 224 and aninductor 226 electrically connected in parallel with the secondcapacitor 224. The second capacitor 224 and the inductor 226 are eachelectrically connected with the output end 218 and the antenna 220.

In operation, when the transmitter device 200 is located within one ofthe instrument thimbles 86 (FIG. 6), the neutron detector 210 absorbsneutrons, causing electrons to migrate outwardly and thus create acurrent. Accordingly, the neutron detector 210, and thus the transmitterdevice 200, is advantageously self-powered (i.e., devoid of a separatepowering mechanism). As the neutron detector 210 generates a current, itcharges the first capacitor 212.

FIG. 8 shows a graph of voltage V₁ versus time measured at the firstcapacitor 212. As shown, the voltage V₁ increases until a voltage V_(b)is reached. The voltage V_(b) is the breakdown voltage of the gasdischarge tube 214. Once the breakdown voltage V_(b) is reached, the gasdischarge tube 214 becomes conductive such that the input end 216 andthe output end 218 electrically connect the first capacitor 212 to theantenna 220 and the oscillator circuit 222. The oscillator circuit 222is an inherently unstable circuit. As such, when the breakdown voltageV_(b) is reached, an intense oscillation is triggered in the oscillatorcircuit 222 for a short period of time.

FIG. 9 shows a graph of voltage V₂ versus time measured in theoscillator circuit 222. As shown, the voltage V₂ generally begins atzero volts, oscillates for a relatively short period of time, andthereafter returns to zero volts before repeating the cycle. Thedampening of the oscillations is due to energy being dissipated byelectromagnetic emissions from the antenna 220 and resistive losses.Accordingly, the oscillator circuit 222 pulses the antenna 220, whichemits a wireless signal.

It will be appreciated that the period between the pulsed signalsemitted by the antenna 220 corresponds inversely to the neutron fluxdetected by the neutron detector 210. More specifically, the currentgenerated by the neutron detector 210 is directly proportional to theneutron flux within the instrument thimble 86 (FIG. 6), and thebreakdown voltage V_(b) is relatively constant. As such, the periodbetween pulses (see, for example, t₁ in FIG. 9) is also inverselyproportional to the neutron flux within the instrument thimble 86 (FIG.6). Therefore, a suitable wireless receiver receiving the signal emittedby the antenna 220 can readily be calibrated to determine the neutronflux within the instrument thimble 86 (FIG. 6). Additionally, the energyof the pulsed transmissions of the antenna 220 remains essentially thesame even if the reactor core power is very low. The pulses simply occurless often. Furthermore, because the frequency of the transmitter device200 is independent of pulse operation, a device designer is able toselect the frequency of the transmitter device 200. This advantageouslyfacilitates the use of many different transmitter devices at differentlocations in the fuel assembly 80, and in other fuel assemblies in thecore. An operator would be able to identify each individual transmitterdevice by its associated frequency, which is dependent on the values ofthe capacitance of the second capacitor 224 and the inductance of theinductor 226. Accordingly, environmental conditions such as neutron fluxare advantageously able to be monitored wirelessly at many differentlocations within the fuel assembly 80.

FIG. 10 shows a schematic circuitry diagram of another transmitterdevice 300, in accordance with another non-limiting embodiment of thedisclosed concept. As shown, the transmitter device 300 is structuredsimilar to the transmitter device 200 (FIG. 7), and like components arelabeled with like reference numbers. For ease of illustration andeconomy of disclosure, only the antenna 320 and the oscillator circuit322 are indicated with reference numbers. However, as shown, theoscillator circuit 322 of the transmitter device 300 further includes aresistance temperature detector 328 electrically connected in serieswith the inductor 326 and electrically connected to the second capacitor324. The resistance temperature detector 328 increases its electricalresistance as the temperature of the environment in which it is locatedincreases. In accordance with one aspect of the disclosed concept, theresistance temperature detector 328 alters the signal emitted by theantenna 320 in a detectable way. More specifically, the amplitude decayrate of the voltage of the oscillator circuit 322 will be altered withthe inclusion of the resistance temperature detector 322. Accordingly,the change in the amplitude decay rate measured by a suitable wirelessreceiver will allow an operator to readily determine a given temperatureat a location within the instrument thimble 86 (FIG. 6). It follows thatthe transmitter device 300 is advantageously able to provide anindication to an operator of neutron flux (i.e., in the same manner asthe transmitter device 200 shown in FIG. 7) and also temperature withinthe instrument thimble 86 (FIG. 6).

FIGS. 11 and 12 show schematic circuitry diagrams of two othertransmitter devices 400, 500, respectively, in accordance with othernon-limiting embodiments of the disclosed concept. As shown, thetransmitter devices 400, 500 are structured similar to the transmitterdevices 200, 300 (FIGS. 7 and 10), and like components are labeled withlike reference numbers. For ease of illustration and economy ofdisclosure, only the antennas 420 and the oscillator circuits 422, 522are identified with reference numbers. As shown in FIG. 11, theoscillator circuit 422 further includes a second inductor (e.g., withoutlimitation, variable inductor 430) electrically connected in series withthe first inductor 426 and the resistance temperature detector 428.Furthermore, the variable inductor 430 is electrically connected to withthe second capacitor 424. As shown in FIG. 12, the oscillator circuit522 further includes a variable capacitor 532 electrically connected inparallel with the second capacitor 524. The variable capacitor 532 isalso electrically connected to the inductor 526 and the resistancetemperature detector 528. Advantageously, environmentally inducedchanges in the electrical values of either the variable inductor 430 orthe variable capacitor 532 will produce a detectable shift in the pulsetransmission frequency.

It will be appreciated that the transmitter devices 400, 500 areadvantageously able to provide an indication to an operator of up tothree environmental conditions within the instrument thimble 86 (FIG.6). For example, the transmitter devices 400, 500 each, via the emittedsignals of the respective antennas 420, 520, are each able tocommunicate to a wireless receiver data corresponding to the neutronflux and the temperature within the instrument thimble 86 (FIG. 6) inthe same manner as the transmitter device 300, discussed above.Additionally, the variable inductor 430 (FIG. 11) and the variablecapacitor 532 (FIG. 12) are each structured to alter the frequency ofthe emitted signal of the respective antennas 420, 520 in a detectableway. The altered frequency provides a mechanism by which a thirdenvironmental condition (e.g., without limitation, pressure, totalneutron dose of a fuel rod over time, water flow rate) can be measuredby the transmitter devices 400, 500 and reported wirelessly to asuitable receiver. For example, the pressure within a fuel rod maycreate a deformation that causes a movement near a coil of the variableinductor 430 to cause a detectable frequency shift in the emitted signalof the antenna 420, thus allowing the pressure to be monitoredwirelessly.

FIG. 13 shows a schematic circuitry diagram of another transmitterdevice 600, in accordance with another non-limiting embodiment of thedisclosed concept. As shown, the transmitter device 600 is structuredsimilar to the transmitter devices 200, 300, 400, 500 (FIGS. 7 and10-12), and like components are labeled with like reference numbers.More specifically, the transmitter device 600 includes a neutrondetector 610, a capacitor 612, a gas discharge tube 614, an antenna 620,and an oscillator circuit 622 that each perform the same functions asthe respective components of the transmitter devices 200, 300, 400, 500(FIGS. 7 and 10-12). As shown, the transmitter device 600 furtherincludes a number of Marx bank stages (e.g., two Marx bank stages 642,644 are shown) electrically connected between the neutron detector 610and the gas discharge tube 614. It will be appreciated that any suitablealternative number of Marx bank stages may be employed ahead of a gasdischarge tube (i.e., and after a neutron detector) in order to performthe desired function of enhancing circuit performance. The Marx bankstages 642, 644 each include a respective capacitor 646, 648, arespective first resistor 650, 652, a respective second resistor 654,656, and a respective gas discharge tube 658, 660.

It will be appreciated that a method of measuring a number ofenvironmental conditions with a transmitter device 200, 300, 400, 500,600 includes the steps of detecting neutron flux with a neutron detector210, 610 storing energy in a capacitor 212, 612 until a breakdownvoltage V_(b) of a gas discharge tube 214, 614 is reached, and emittinga signal with an antenna 220, 320, 420, 520, 620 corresponding to theneutron flux. The method may further include the steps of pulsing theantenna 220, 320, 420, 520, 620 with an oscillator circuit 222, 322,422, 522, 622 altering the signal emitted by the antenna 220, 320, 420,520, 620 with a resistance temperature detector 328, 428, 528, and/oraltering the signal emitted by the antenna 220, 320, 420, 520, 620 witha variable inductor 430 or a variable capacitor 532.

The novel transmitter devices 200, 300, 400, 500, 600 are able tomeasure the disclosed environmental conditions within the instrumentthimble 86 (FIG. 6) and withstand the relatively harsh operatingconditions for at least two reasons. First, the transmitter devices 200,300, 400, 500, 600 are each advantageously devoid of semiconductors.Second, the transmitter devices 200, 300, 400, 500, 600 generallyinclude only one single powering mechanism (e.g., the respective neutrondetectors (only the neutron detectors 210, 610 are indicated)). Knownattempts at providing a wireless mechanism to communicate data onenvironmental conditions typically require more power than is availablefrom a neutron detector, and/or are not able to withstand the relativelyharsh radiation environment due to the inclusion of semiconductors.Additionally, known devices (not shown) exhibit relatively lowtransmitter power, and as such shutdown completely when the reactorpower is decreased below a critical threshold. The transmitter devices200, 300, 400, 500, 600 are novel in their combination of a self-poweredneutron detector 210, 610 and energy storage capacitor 212, 612 toachieve reasonable transmission power over a wide reactor power range.Furthermore, as discussed, the transmitter devices 400, 500 areadvantageously able to transmit readings on up to three differentenvironmental parameters concurrently from a given sensing locationwithin the instrument thimble 86. Moreover, because all of themonitoring is being done wirelessly, the need for major reactor vesselpenetrations and cabling to monitor environmental conditions is reducedand/or eliminated.

Accordingly, the disclosed concept provides for an improved (e.g.,without limitation, better able to monitor environmental conditionswithin an instrument thimble 86) nuclear reactor system, transmitterdevice 200, 300, 400, 500, 600 therefor, and associated method ofmeasuring environmental conditions.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof

What is claimed is:
 1. A transmitter device comprising: a neutrondetector structured to detect neutron flux; a capacitor electricallyconnected in parallel with said neutron detector; a gas discharge tubecomprising an input end and an output end, said input end beingelectrically connected with said capacitor; and an antenna electricallyconnected to said output end, said antenna being structured to emit asignal corresponding to the neutron flux.
 2. The transmitter device ofclaim 1 further comprising an oscillator circuit electrically connectedwith said output end and said antenna; and wherein said oscillatorcircuit is structured to pulse said antenna.
 3. The transmitter deviceof claim 2 wherein said oscillator circuit comprises a second capacitorand an inductor electrically connected to said second capacitor; andwherein said second capacitor and said inductor are each electricallyconnected with said antenna.
 4. The transmitter device of claim 3wherein said oscillator circuit further comprises a resistancetemperature detector electrically connected in series with saidinductor; and wherein said resistance temperature detector is structuredto alter the signal emitted by said antenna.
 5. The transmitter deviceof claim 3 wherein said oscillator circuit further comprises a secondinductor electrically connected in series with said inductor; andwherein said second inductor is structured to alter the signal emittedby said antenna.
 6. The transmitter device of claim 5 wherein saidsecond inductor is a variable inductor.
 7. The transmitter device ofclaim 1 further comprising a number of Marx bank stages electricallyconnected between said neutron detector and said gas discharge tube. 8.The transmitter device of claim 1 wherein said transmitter device isdevoid of a semiconductor.
 9. The transmitter device of claim 1 whereinsaid transmitter device comprises only one single powering mechanism;and wherein said one single powering mechanism is said neutron detector.10. A nuclear reactor system comprising: a fuel assembly having aninstrument thimble; and a transmitter device comprising: a neutrondetector disposed within said instrument thimble, said neutron detectorbeing structured to detect neutron flux, a capacitor electricallyconnected in parallel with said neutron detector, a gas discharge tubecomprising an input end and an output end, said input end beingelectrically connected with said capacitor, and an antenna electricallyconnected to said output end, said antenna being structured to emit asignal corresponding to the neutron flux.
 11. The nuclear reactor systemof claim 10 wherein said transmitter device further comprises anoscillator circuit electrically connected with said output end and saidantenna; and wherein said oscillator circuit is structured to pulse saidantenna.
 12. The nuclear reactor system of claim 11 wherein saidoscillator circuit comprises a second capacitor and an inductorelectrically connected to said second capacitor; and wherein said secondcapacitor and said inductor are each electrically connected with saidantenna.
 13. The nuclear reactor system of claim 12 wherein saidoscillator circuit further comprises a resistance temperature detectorelectrically connected in series with said inductor; and wherein saidresistance temperature detector is structured to alter the signalemitted by said antenna.
 14. The nuclear reactor system of claim 12wherein said oscillator circuit further comprises a second inductorelectrically connected in series with said inductor; and wherein saidsecond inductor is structured to alter the signal emitted by saidantenna.
 15. The nuclear reactor system of claim 14 wherein said secondinductor is a variable inductor.
 16. The nuclear reactor system of claim10 wherein said transmitter device is devoid of a semiconductor.
 17. Amethod of measuring a number of environmental conditions with atransmitter device, said transmitter device comprising a neutrondetector, a capacitor electrically connected in parallel with saidneutron detector, a gas discharge tube comprising an input end and anoutput end, and an antenna electrically connected to said output end,said input end being electrically connected with said capacitor, themethod comprising the steps of: detecting neutron flux with said neutrondetector; storing energy in said capacitor until a breakdown voltage ofsaid gas discharge tube is reached; and emitting a signal with saidantenna corresponding to the neutron flux.
 18. The method of claim 17wherein said transmitter device further comprises an oscillator circuitelectrically connected with said output end and said antenna; andwherein the method further comprises: pulsing said antenna with saidoscillator circuit.
 19. The method of claim 18 wherein said oscillatorcircuit comprises a second capacitor, an inductor electrically connectedto said second capacitor, and a resistance temperature detectorelectrically connected in series with said inductor; wherein said secondcapacitor and said inductor are each electrically connected with saidantenna; and wherein the method further comprises: altering the signalemitted by said antenna with said resistance temperature detector. 20.The method of claim 18 wherein said oscillator circuit comprises asecond capacitor, an inductor electrically connected to said secondcapacitor, and a second inductor electrically connected in series withsaid inductor; wherein said second capacitor and said inductor are eachelectrically connected with said antenna; and wherein the method furthercomprises: altering the signal emitted by said antenna with said secondinductor.